The fundamental design of fans and fan blades has been largely unchanged for many years. Many conventional fans consist of fan blades and a central structure to which the fan blades are connected (often referred to as a “spider”). Historically, both the spider and the associated fan blades have been overbuilt, resulting in heavy and often inefficient fan and fan blade designs. Due at least in part to market and industry conditions, improving such designs has not been necessary. However, with increasing competition and shrinking profit margins, a manufacturer of fans must address the problems associated with weight and inefficiency in order to remain competitive in the industry.
One significant challenge in fan design is a high manufacturing cost per unit. Inefficient use of material and multiple manufacturing steps contribute greatly to this challenge. For example, in order to provide sufficient strength and rigidity, conventional metal fans having a 16-24 inch diameter typically have a steel spider having a thickness ranging between 0.059 inches and 0.075 inches, and have steel or aluminum fan blades with a minimum thickness of 0.025 inches and 0.032 inches, respectively. The width of blades for such fans is greater than 8.0 inches and is often as wide as 9.5 inches. Combined with a heavy center steel hub, such features result in an overweight fan assembly. To drive down the manufacturing cost per unit and to remain competitive in the industry, new fan designs must be employed to address these fan limitations without any decrease in product performance.
Another example of a costly design problem in the fan industry is the balancing procedure necessary for many fans after assembly. Commonly, counterweights are added to the fan in order to correct an imbalance due to blade weight variation or other assembly weight variation. In some cases, two or more balancing tests must be run to determine whether the fan assembly has been adequately balanced. The balancing procedure for fans consumes valuable manufacturing time, is often very labor and material intensive, and increases the manufacturing cost of the fan.
In light of the problems and limitations of the prior art described above, a need exists for a fan that has a reduced amount of material so to minimize material costs, has the same or improved fluid moving capabilities as conventional fans, requires less balancing steps following fan assembly or that requires no after-assembly balancing, and that reduces one or more manufacturing costs of the fan. Each embodiment of the present invention achieves one or more of these results.